Various types of analytical tests related to patient diagnosis and therapy can be performed by analysis of a liquid sample taken from a patient's infections, bodily fluids or abscesses. These assays are typically conducted with automated clinical analyzers onto which tubes or vials containing patient samples have been loaded. The analyzer extracts liquid sample from the vial and combines the sample with various reagents in special reaction cuvettes or tubes. Usually the sample-reagent mixture is incubated or otherwise processed before being analyzed. Analytical measurements are often performed using a beam of interrogating radiation interacting with the sample-reagent mixture to generate turbidimetric, fluorometric, absorption readings or the like. The readings allow determination of end-point or rate values from which an amount of analyte related to the health of the patient may be determined using well-known calibration techniques.
There is incentive for increasing the efficiency of throughput of patient samples and one approach has been to vary the method for scheduling the operation of various assay devices on sample-reagent mixtures. Assay devices include aspiration probes for samples and reagents, mixing and washing stations, incubation and analytical stations, and the like. Reagent is usually initially dispensed into a reaction container or cuvette and sample is then added. The reagent-sample mixture is then transported from one assay device to another depending upon the assay being performed. The assay devices are operated under control of a computer having software programs used by those skilled in the art of computer-based electromechanical control programming to perform assays with related assay devices and assay operations given the identity of a patient sample, assay requests, and the like.
A number of different methods for controlling transportation between assay devices have been employed. One method operates all assay devices within a fixed cycle or length of time so that overall analyzer throughput is constant. Alternately, the assay devices may be controlled so that cycle times vary depending on the assay being conducted, a method known as “adaptive scheduling”. The complexity of adaptive scheduling can adversely affect the throughput of the analyzer as the number of assay devices required for sophisticated assay increase. Various methods have been developed to improve both of these approaches.
U.S. Pat. No. 7,015,042 discloses a fixed-cycle process whereby incoming samples are partitioned into groups in accord with the length of time required for the assay to be completed or in accord with the pattern of reagent addition(s) taken with length of time required for the assay to be completed. Medium length time assays are completed, removed from a reaction carousel and replaced by shorter length time assays during a single operational cycle in which longer length assays are also completed.
U.S. Pat. No. 6,723,288 discloses a fixed cycle analyzer having an indexing drive for rotating a reaction carousel in a constant direction a predetermined numbers of incremental steps. The length of the circumference of carousel, the separation distance between reaction ports, the number of reaction ports and the number of increments per indexing are selected so that any given cuvette port returns to its original starting position after a fixed number of incremental steps. Throughput is determined by the fixed number of incremental steps multiplied by the sum of dwell time at each assay device and the time required for a stepwise movement.
U.S. Pat. No. 5,846,491 discloses an analyzer having a fixed cycle time for certain assay resources having a first fixed cycle time during which that assay resource is available to perform a predetermined operation on a sample-containing reaction vessel. Each of the other assay resources is also assigned a fixed cycle time, where the first cycle time is an integral multiple of the second cycle time, the two cycle times desirably being different from one another. As a result, control scheduling is simplified.
U.S. Pat. No. 5,576,215 discloses a process wherein the analyzer is operated in accordance with a schedule developed by a scheduler routine. The scheduler routine determines interval periods between operations performed by the analyzer on each biological sample as a function of an entered load list unless a fixed interval period between the operations is required and schedules instrument system operations and the determined interval periods. The analyzer assays the samples by operating its instrument systems in accordance with the developed schedule.
U.S. Pat. No. 5,252,612 discloses an analyzer that incrementally indexes a sample in a first direction in a set of increments wherein each increment represents a movement of the samples an amount corresponding to a number of samples. The movement of samples within all of the increments in the set of increments added together produces a sum which is a net move of the sample support an amount of samples equal to a second plurality of holders greater than one holder and less than the first plurality such that the greatest common factor between the second plurality and the first plurality is the number of increments in the set. Such a system enables separation of logical space from physical space in the system, allowing freedom in placement of assay devices while permitting proper sequencing of operations both in space and in time.
From the above descriptions of the art, it is apparent that, while throughput improvements have been made in controlling assay devices, the ability to quickly and efficiently operate an analyzer at different throughputs depending upon the assay load presented to the analyzer has not been achieved. In particular so-called “fixed cycle” analyzer can operate at only a single throughput, regardless of whether a larger number or a smaller number of assays need to be performed. Further, so-called “variable cycle” analyzers that rely on adaptive scheduling have a “variable throughput” but only as a consequence of the different types of assays to be performed, again, regardless of whether at larger number or a smaller number of assays need to be performed.